SERVICE INSTRUCTION
652 Oliver Street Williamsport, PA. 17701 U.S.A. Tel. 570­323­6181 Fax. 570­327­7101 www.lycoming.com DATE: November 10, 2011 Service Instruction No. 1143C (Supersedes Service Instruction No. 1143B, Supplement No. 2, 3 and 4 to Service Instruction No. 1143B and Service Letter No. L217) Engineering Aspects are FAA Approved SUBJECT: Counterweight Bushing Inspection, Replacement, and Special Tooling Upgrades MODELS AFFECTED: All Lycoming piston aircraft engines with dynamic counterweights TIME OF COMPLIANCE: During engine overhaul. NOTE Incomplete review of all the information in this document can cause errors. Read the entire Service Instruction to make sure you have a complete understanding of the requirements. This Service Instruction includes all of the necessary information to examine, remove, prepare, and install counterweight bushings. Because of counterweight manufacturing changes, some modifications to existing tools used to replace counterweight bushings could be necessary. Instructions for tooling modifications also are included in Appendix A of this Service Instruction NOTE Previous supplements are included in this revision of the Service Instruction. Overview NOTE Counterweight bushings must always be replaced with new counterweight bushings during engine overhaul or whenever counterweight bushings are removed. All counterweight bushings must be replaced at the same time. Replacement of counterweight bushings is to be done in the following sequence of tasks: 1. 2. 3. Task: Section to refer to in this Service Instruction Remove the bushing Identify the correct spacers that are necessary to install the counterweight bushings It could be necessary to make special tools to do the bushing replacement Counterweight Bushing Removal Counterweight Spacer Identification MO 12 Appendix A – Special Tools Used for Counterweight Bushing Replacement ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 1 of 19 C ©2011 Avco Corporation. All Rights Reserved. Lycoming Engines is a division of Avco Corporation. Task: Section to refer to in this Service Instruction Counterweight Bushing Bore Inspection 6. 7. 8. Examine the bushing bore on the counterweight Install the bushing pair on the counterweight Do grinding on the bushing bore Examine finished bushings Examine installed counterweight bushing 9. Do the balancing procedure Counterweight Balancing Procedure 4. 5. Counterweight Bushing Installation Inner Diameter Bushing Bore Grinding Procedure Inspection of Finished Counterweight Bushings Counterweight Bushing Installation Inspection Counterweight Bushing Removal Tools to be used include:
· Arbor press spindle
· Counterweight bushing driver ST­92 (Appendix A)
· Counterweight fixture assembly ST­93 (Appendix A)
· Depth control spacer ST­93­3 (Appendix A)
· Depth control spacer ST­93­5 (Appendix A) 1. Put the counterweight flat on the table, square and level against the arbor press spindle. 2. Install the applicable depth control spacer ST­93­3 or ST­93­5 in the counterweight bushing bore. 3. Use the arbor press spindle and counterweight bushing driver ST­92 to press both bushings out from one side of the counterweight. Refer to Figure 1. 4. Turn the counterweight over. 5. Use the arbor press spindle and counterweight bushing driver ST­92 to press out the remaining bushings. Refer to the “Counterweight Bushing Bore Inspection” procedure in this Service Instruction. Figure 1 Counterweight Bushing Removal/Installation Using the Counterweight Fixture Assembly ST­93 (Appendix A) and the Counterweight Bushing Driver ST­92 (Appendix A)
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 2 of 19 C S.I. 1143 Counterweight Spacer Identification The counterweights with the new dimensions all have new part numbers. To identify new counterweights that have replaced superseded counterweights, refer to the latest revision of Service Instruction No. 1012. Some new counterweights have a new suffix on the end of the part number that identifies counterweights that can only be installed on direct drive Lycoming engines. Dimension A in Figure 2 is the distance from the center line of the counterweight bushing bore to the flat edge of the counterweight. This dimension is used to identify the thickness of the spacer, Dimension B. Refer to Figure 2 and Figure A­1. Figure 2 Dimension “A” and “B” on the Counterweight Table 1 shows Dimensions A and B values in Figure 2 for the counterweight part numbers in addition to the corresponding spacers. Spacers are used to align the bushing bore of the counterweight with the fixture tool P/N 64878. NOTE In Table 1, some of the counterweights that have been made to the new specifications do not have the same Dimension A as superseded counterweights. Counterweight Part No. 71904 LW­19225D LW­19225E 14U22538 71905 LW­19226D LW­19226E 14U22539 72801 LW­19227D** LW­19227E TABLE 1 COUNTERWEIGHT SPACER DIMENSIONS Dimension A Dimension B ± 0.010 in. ±0.0005 in. Spacer Detail (0.254 mm) (0.0127 mm) Part No. * Figure 2 Figure 2 (in.) (mm) (in.) (mm) 12
0.825 21.0 0.425 10.8 27
0.855 21.7 0.395 10.0 17
0.875 22.2 0.375 9.5 27 0.855 22.2 0.395 10.0 12
0.825 21.0 0.425 10.8 27
0.855 21.7 0.395 10.0 17
0.875 22.2 0.375 9.5 32 0.835 21.2 0.415 10.5 10
0.715 18.2 0.535 13.6 28
0.740 18.8 0.510 13.0 30 0.761 19.3 0.489 12.4 MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 Weight Minimum (Lbs.) 1.796 1.796 1.796 1.796 1.752 1.756 1.756 1.756 1.846 1.846 1.846 PAGE NO. REVISION 3 of 19 C (Kg) 0.81 0.81 0.81 0.81 0.79 0.80 0.80 0.80 0.84 0.84 0.84
S.I. 1143 TABLE 1 COUNTERWEIGHT SPACER DIMENSIONS Dimension A Dimension B ± 0.010 in. ±0.0005 in. Weight Minimum Counterweight Spacer Detail (0.254 mm) (0.0127 mm) Part No. Part No. * Figure 2 Figure 2 (in.) (mm) (in.) (mm) (Lbs.) (Kg) 72534 13
0.950 24.1 0.300 7.6 2.246 1.02 LW­19213 29 0.965 24.5 0.285 7.2 2.246 1.02 73643 15
0.805 20.4 0.445 11.3 2.212 1.00 LW­19211 12 0.825 21.0 0.425 10.8 2.212 1.00 73644 11
0.741 18.8 0.509 12.9 2.166 .098 LW­19210 30 0.761 19.3 0.489 12.4 2.166 .098 73812 16
0.908 23.1 0.342 8.7 2.266 1.03 LW­19212 31 0.923 23.4 0.327 8.4 2.266 1.03 74901 20 0.720 18.3 0.530 13.5 1.470 0.67 75636 20 0.720 18.3 0.530 13.5 1.600 0.73 75637 17 0.875 22.2 0.395 9.5 1.678 0.76 76044 18 0.730 18.5 0.520 13.2 1.810 0.82 78988 18
0.730 18.5 0.520 13.2 1.600 0.73 14U22539 32 0.835 21.2 0.415 10.5 1.756 0.80 * Spacers are used to align the bushing bore of the counterweight with the grinding fixture P/N 64878. ** Use spacer No. 30 and 0.001 in. (0.025 mm) thick shim stock to make 0.490 in. (12.45 mm) spacer thickness when grinding the bushings in an LW­19227 counterweight. Counterweight Bushing Bore Inspection 1. Visually examine the bushing bore. The bore must be smooth and without scratches, tool marks, galling or other surface damage. If any evidence of surface damage is found, replace the counterweight. 2. Measure the bushing bore diameter on the counterweight. a. If the counterweight has a letter B marking, the bushing bore diameter must be between 0.9384 and 0.9392 in. (23.835 and 23.856 mm). b. If the counterweight does NOT have a letter B marking, the bushing bore on the counterweight is smaller and must be between 0.9369 and 0.9377 in. (23.797 and 23.818 mm). CAUTION DO NOT INCREASE THE DIAMETER OF THE BUSHING BORE ON A COUNTERWEIGHT. THIS ENLARGEMENT CAN CAUSE ENGINE DAMAGE BECAUSE IT WILL DECREASE THE SNAP RING GROOVE DEPTH IN THE BUSHING BORE ON THE COUNTERWEIGHT. 3. If the bushing bore on the counterweight is not within the tolerances shown above, replace the counterweight. Some counterweights must be replaced as a matched set. Refer to the latest revision of Service Instruction No. 1012 to identify the correct replacement counterweights and whether they must be replaced as a matched set.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 4 of 19 C S.I. 1143 NOTE The magnetic particle inspection must be done by a qualified and certified technician as per the latest revision of Service Instruction No. 1285. 4. Examine the counterweight for cracks; use the magnetic particle inspection method. If cracks are found, replace the counterweight. Counterweight Bushing Installation Tools and parts to be used for this procedure include:
· Counterweight bushing driver ST­92 (Appendix A)
· Counterweight fixture assembly ST­93 (Appendix A)
· Two locating pins ST­93­2 (Appendix A)
· Depth control spacer ST­93­3 (Appendix A)
· Depth control spacer ST­93­5 (Appendix A)
· Four new dynamic counterweight bushings shown in Table 2 NOTE Part numbers for dynamic counterweight bushings are identified with a suffix letter at the end of the part number. TABLE 2 COUNTERWEIGHT BUSHING PART NUMBERS Bushing Part Number Outer Diameter (OD) Dimensions Inches Millimeters 71903­A 0.9390 to 0.9395 23.85 to 23.86 71903­B 0.9405 to 0.9410 23.89 to 23.90 CAUTION SPACERS SUPPLIED WITH THE COUNTERWEIGHT FIXTURE ASSEMBLY ST­93 ARE USED TO CONTROL THE DEPTH THAT THE BUSHINGS ARE DRIVEN INTO THE COUNTERWEIGHT. THE BUSHING MUST BE FLUSH TO 0.002 IN. (0.051 MM) FROM PROTRUSION INTO THE SLOT OF THE COUNTERWEIGHT. 1. Use four new correct sized counterweight bushings to be installed; refer to Table 2 to identify the correct counterweight bushings. 2. Measure the center­to­center distance of the bushing bore in the counterweight. 3. Make a selection of two holes in the counterweight fixture assembly ST­93 that agree with the measured center­to­center distance. 4. Install two locating pins ST­93­2 in the two holes of the counterweight fixture assembly ST­93. 5. Install the correct spacer ST­93­3 (0.370 in. or 94 mm) thick or ST­93­5 (0.440 in. or 11.2 mm) on the counterweight. Refer to Figure 1. 6. Put the counterweight with the two locating pins ST­93­2 in the bushing bores on the counterweight fixture assembly ST­93.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 5 of 19 C S.I. 1143 7. Use an arbor press and counterweight bushing driver ST­92 to press the two new counterweight bushings into place. 8. Remove the spacer (ST­93­3 or 93­5). 9. Turn the counterweight over. 10. Install the correct spacer ST­93­3 or ST­93­5 on the counterweight. Refer to Figure 1. 11. Use an arbor press and counterweight bushing driver ST­92 to press the two new counterweight bushings into place. 12. Refer to the “Inner Diameter Bushing Bore Grinding Procedure” in this Service Instruction. Inner Diameter Bushing Bore Grinding Procedure Tools and parts to be used for this procedure include:
· Fixture P/N 64878 with a 3/4 x 1 x 1/4 in. (19.05 x 25.4 x 6.35 mm) grinding wheel
· Three 1/4­20 socket head screws
· One knurled head screw
· One small locating pin P/N 64878­2
· One larger locating pin P/N 64878­6
· Locating clamp P/N 64878­23
· Metal block P/N 64878­21 NOTE The fixture P/N 64878 does not have any mounts or pre­drilled holes in its base to enable flexible installation on any grinding machine without interference from pre­drilled holes or mounts. This procedure is used to make the inner diameter of the new bushings of the correct size and surface finish for correct counterweight bushing installation and operation. NOTE You must follow the steps of this procedure in sequence. Do not use any other procedure or method for grinding the bushings. 1. Refer to Table 1 to identify the correct spacer to be used for the corresponding counterweight. 2. Install the fixture P/N 64878 on the faceplate of an internal grinding machine. 3. Make sure that the 1/8 in. (3.18 mm) diameter hole in the center of the fixture is concentric with the center of the face plate on the internal grinding machine. Concentricity must be held to within ± 0.0005 in. (± 0.0127 mm). Refer to Figure 3.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 6 of 19 C S.I. 1143 Figure 3 Counterweight and 64878 Fixture Assembled on an Internal Grinding Machine 4. Install the correct spacer (identified in Table 1 of this Service Instruction) on the fixture P/N 64878. 5. Attach the spacer securely to the alignment bar of the fixture with three, 1/4­20 socket head screws. NOTE The small locating pin P/N 64878­2 is used to align the counterweight with an unground counterweight bushing. The larger locating pin P/N 64878­6 is used to align the fixture P/N 64878 with ground­to­size counterweight bushing bore distances on the counterweights. 6. Install and rotate the smaller locating pin P/N 64878­2 in a position to install one set of counterweight bushings on the centerline of the fixture. 7. Lock the locating pin in this position by tightening the 10­32 socket head screw that attaches the locating clamp P/N 64878­23. 8. Make sure the mating surfaces of the counterweight and fixture P/N 64878 are clean. 9. Install the counterweight on the fixture P/N 64878 as shown in Figure 3. NOTE In the next step, when tightening the knurled head screw, do not tighten past the point where the screw can enter the slot in the counterweight. If the threaded­end of the knurled head screw starts to enter the slot, install the metal block P/N 64878­21 on the end of the knurled head screw. 10. Tighten the knurled head screw to attach the counterweight securely against the spacer.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 7 of 19 C S.I. 1143 11. Adjust the fiber block of the hold down clamp over the center of the counterweight. 12. Tighten the socket head screw to securely attach the counterweight to the fixture. 13. Grind the inside diameter of both counterweight bushings to between 0.7485 to 0.7505 in. (19.011 to 19.063 mm) in diameter. The surface of the ground bushing must be 15 micro­inches (0.000381 mm). 14. Remove the counterweight from the fixture. 15. Remove the small locating pin P/N 64878­2 from the fixture. 16. Install the larger locating pin P/N 64878­6 in the hole opposite from where the smaller locating pin P/N 64878­2 had been installed. 17. Rotate the larger locating pin P/N 64878­6 to align the unground bushings with the centerline of the fixture. 18. Do steps 7 through 17 again. 19. Remove the larger locating pin from the fixture. 20. Examine the finished counterweight bushings. Refer to the section “Inspection of Finished Counterweight Bushings” in this Service Instruction. Inspection of Finished Counterweight Bushings Tools and parts to be used for this procedure include:
· Counterweight bushing location gage ST­94 (Appendix A)
· Relieved locating pin ST­94­2 (Appendix A)
· Solid locating pin ST­94­3(Appendix A)
· Counterweight squareness gage ST­91(Appendix A)
· Spacers: ST­91­7, ST­91­8, ST­91­9, ST­91­10, ST­91­11, ST­91­12, ST­91­13, ST­91­14 (Appendix A)
· Gauging arbors ST­91­3 (Appendix A)
· Depth gage NOTE The magnetic particle inspection must be done by a qualified and certified technician as per the latest revision of Service Instruction No. 1285. 1. Examine the newly ground counterweight bushings using the magnetic particle inspection method to identify any grinding cracks in the finished bushing. Replace any bushings with a crack. 2. To set up the counterweight bushing location gage ST­94: a. Install the relieved locating pin ST­94­2 in the center hole on the set­master with the locating diameters in the vertical position as shown in Figure 4. b. Install the solid locating pin ST­94­3 in the outside hole that has the same center to center distance as the counterweight bushing bores. The relieved locating pin ST­94­2 can stay permanently installed in the center hole with the solid locating pin ST­94­3 moved as necessary to adapt to the counterweight under inspection. c. If the locating pins do not install into the newly ground bushing, the bores are not in the correct location; the bushings must be replaced and reground again. If the locating pins install correctly, do the next step.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 8 of 19 C S.I. 1143 Figure 4 Depth Gage Adjusted with Set­Master Preparatory to Checking Line Position of Counterweight Bushings 3. Use the counterweight bushing location gage ST­94 to measure the finished bushing bores on the counterweight for correct location. 4. Use the counterweight bushing location gage ST­94 to measure the distance from the center of the bushing bore to the flat edge of the counterweight. 5. Use either set­master ST­94­5 or the new set­master ST­94­10 as follows: a. Put the set­master over the locating pins of the counterweight bushing location gage ST­94 (Figure 4). b. Do a preload of the depth gage approximately 0.010 in. (0.25 mm). c. Set the dial gage to “0” with the plunger on the applicable step of the spacer set­master. As shown in Figure A­2, the steps are identified by Dimension A from Table 1. d. Remove the set­master. e. Install the counterweight over the locating pins. f. Set the depth gage through the counterweight bushing location gage ST­94 and onto the counterweight and take a measurement. Refer to Figure 5. g. There must not be more than a ± 0.004 in. (± 0.10 mm) difference between the depth gage measurement on the counterweight and the measurement taken with the set­master.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 9 of 19 C S.I. 1143 Figure 5 Checking Center Line Position of Counterweight Using the Counterweight Bushing Location Gage ST­94 6. If erratic or excessively “out of tolerance” measurements are found: a. Remove the counterweight from the locating pins. b. Install the counterweight on the counterweight squareness gage ST­91 so that the opposite inner face of the counterweight is against the counterweight squareness gage ST­91. c. Only one of the inner faces of the counterweight is square with the bushing bores. d. Take the depth measurements again. 7. Install the correct spacer, (ST­91­7, ST­91­8, ST­91­9, ST­91­10, ST­91­11, ST­91­12, ST­91­13, ST­91­14) and the counterweight on the counterweight squareness gage ST­91. Refer to Figure A­3 and Table A­2 for spacer application. 8. Press the counterweight squarely against the spacer and tighten the knurled screw to attach the counterweight firmly against the locating surface of the counterweight squareness gage ST­91. 9. Install the gauging arbors P/N ST­91­3 through each of the finished bushings as shown in Figure 6. 10. Put the counterweight squareness gage ST­91 on a surface plate and measure both ends of each arbor as shown in Figure 6. 11. Turn the counterweight squareness gage ST­91 over on its adjacent side and again measure both ends of the gaging arbors (Figure 7). 12. The difference in measurements from one end of the gaging arbor to the other must not be more than 0.003 in. (0.076 mm) per inch (25.4 mm) in any instance. 13. Refer to the “Counterweight Balancing Procedure” in this Service Instruction.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 10 of 19 C S.I. 1143 Figure 6 Checking Parallel and Squareness of Counterweight Bushings with Counterweight Squareness Gage ST­91 – Vertical Position Figure 7 Checking Parallel and Squareness of Counterweight Bushings with Counterweight Squareness Gage ST­91 ­ Horizontal Position Counterweight Bushing Installation Inspection Tools to be used include:
· Counterweight dial bore gage ST­73 (Appendix A)
· Micrometer or set ring 1. Calibrate the counterweight dial bore gage ST­73 with a micrometer or set ring. 2. Measure the diameter of each counterweight bushing using the counterweight dial bore gage ST­73. The diameter must be between 0.7485 and 0.7505 in. (19.01 and 19.06 mm). 3. The out­of­round must not be more than 0.0005 in. (0.0127 mm).
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 11 of 19 C S.I. 1143 NOTE Evidence of bushing wear includes out­of­roundness on the inside diameter. 4. If the diameter of the bushing is out­of­round, oversized, or out­of­tolerance, replace ALL of the bushings in the counterweight. Start with the “Counterweight Bushing Removal” procedure in this Service Instruction. Counterweight Balancing Procedure Tools and parts to be used for this procedure include:
· Counterweight balancing weight ST­95 (Appendix A)
· Counterweight balancing arbor ST­96 (Appendix A)
· Counterweight balancing arbor ST­96­1 – 3/8 in. (6.35 mm) size (Appendix A)
· Counterweight balancing arbor ST­96­2 – 1/4 in. (9.53 mm) size (Appendix A) Installation of new counterweight bushings can inadvertently change the counterweight balance in relation to its center of gravity. The center of gravity of the counterweight is at the center of the 1/4 in. (6.35 mm) or 3/8 in. (9.53 mm) diameter drilled hole that is between the bushing bores. You must do a check of the counterweight balance after bushings are installed on the counterweight for correct counterweight operation. To do this check: A. Use one of two counterweight balancing arbors ST­96­1 for the 3/8 in. (6.35 mm) size or ST­96­2 for the 1/4 in. (9.53 mm) size. B. Install the counterweight on the correct counterweight balancing arbor (ST­96­1 or ST­96­2). C. Put the counterweight balancing arbor on a pair of balancing ways. D. Make sure each blade of the balancing ways engages the arbor at a point not more than 1.5 in. (38.1 mm) from each end. NOTE The center of both of the balancing arbors (ST­96­1 and ST­96­2) has a taper as compensation for slight variations in the diameter of the hole. The first 1.5 in. (38.1 mm) of each end of the arbor is carefully ground for concentric diameters. E. Record the position of the counterweight and refer to Table 3 to analyze the results: TABLE 3 COUNTERWEIGHT BALANCING RESULTS Results Counterweight stays in any position when it is placed on the counterweight balancing arbor Reference Figure 8 Outcome Counterweight is in perfect balance Figure 8 Counterweight Mounted on ST­96 Arbor for Balancing
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 12 of 19 C S.I. 1143 TABLE 3 COUNTERWEIGHT BALANCING RESULTS Results If the counterweight moves, put the center of a counterweight balancing weight ST­95 not more than 1 in. (25.4 mm) from the center of the arbor. Reference Figure 9 Outcome If the counterweight comes into balance with the addition of this weight, the counterweight balance is satisfactory. Figure 9 Counterweight Balanced by Balancing Weight ST­95 Placed Within One Inch from Center F. If the counterweight does not become balanced with the addition of the counterweight balancing weight ST­95, carefully grind the heavy end at the locations shown in Figure 10. Do the Counterweight Balancing Procedure again. NOTE A weight check of the counterweight is not necessary unless the counterweight has been ground to correct an out­of balance condition. If the counterweight has been ground, it must be in compliance with the minimum weight requirements shown in Table 1. Do not install a counterweight that weighs less than the minimum weight shown in Table 1. Figure 10 Location of Areas on Counterweight for Grinding Record all procedures done to replace the counterweight bushings in the engine logbook.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 13 of 19 C S.I. 1143 APPENDIX A Special Tools Used for Counterweight Bushing Replacement Table A­1 shows a list of special tools used to replace counterweight bushings. Refer to the latest revision of SSP­384 for Lycoming Engines’ complete special tool list. NOTE Tools are available for purchase or rental. TABLE A­1 SPECIAL TOOLS FOR COUNTERWEIGHT BUSHING INSTALLATION ST­73 Gage, Counterweight Dial Bore (.7485/.7505 ID of Bushings) Replace Bushings in Counterweights ­ All engines with counterweights that have bushings except counterweight P/N 77002 ST­91 Gage, Counterweight Squareness (Check Parallel and Squareness of Finished Inside Diameter of Bushing Hole) ­ All engines with counterweights that have bushings except Counterweight P/N 77002 Gauging Arbors Knurled Screw Spacer Spacer Spacer Spacer Spacer Spacer Spacer Spacer Driver, Counterweight Bushing (Remove and Install Bushings) ­ All engines with counterweights that have bushings except Counterweight P/N 77002 Fixture Assembly, Counterweight (Install Bushings in Counterweights) ­ All engines with counterweights that have bushings except Counterweight P/N 77002 Locating Pin Spacer, Control Depth of Bushing ­ 0.370 in. (9.4 mm) thick (detail of ST­93) Spacer, Control Depth of Bushing ­ 0.440 in. (11.2 mm) thick (detail of ST­93)
ST­91­3 ST­91­6 ST­91­7 ST­91­8 ST­91­9 ST­91­10 ST­91­11 ST­91­12 ST­91­13 ST­91­14 ST­92 ST­93 ST­93­2 ST­93­3 ST­93­5 MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 14 of 19 C S.I. 1143 TABLE A­1 SPECIAL TOOLS FOR COUNTERWEIGHT BUSHING INSTALLATION ST­94 Gage, Counterweight Bushing Location (Check Hole Location After Grinding) ­ All engines with counterweights that have bushings except Counterweight P/N 77002 Pin, Relieved Locating Pin, Solid Locating Set­Master Set­Master Weight, Counterweight Balancing (.004 pound ­ Check Balance of Counterweight after Re­ bushing) ­ All engines with counterweights that have bushings except Counterweight P/N 77002 ST­94­2 ST­94­3 ST­94­5 ST­94­10 ST­95 ST­96 Arbor, Counterweight Balancing (Check Balance of Counterweights after Re­bushing) ­ All engines with counterweights that have bushings except Counterweight P/N 77002 Arbor, Counterweight Balancing 3/8 in. (6.35 mm) size Arbor, Counterweight Balancing 1/4 in. (9.53 mm) size Fixture, Grind Bushings in Dynamic Counterweight ­ All engines with counterweight bushings Small Locating Pin Large Locating Pin Metal Block Locating Clamp Fixture Update Kit ST­96­1 ST­96­2 64878 64878­2 64878­6 64878­21 64878­23 64878­50 New Tool Updates and Modifications A new fixture update kit P/N 64878­50 is available for purchase from Lycoming Engines. This kit includes special spacers for the new counterweights. As an alternative, if you do not make a purchase of the new update kit, you can make the necessary spacers from hardened and ground steel using the dimensions shown in Figure A­1. You must make a stamp or do a vibra­peen etch of the correct part number on the surface of each spacer in such a way that will not prevent correct counterweight alignment. NOTE Service Letter No. L217, which had identified counterweight tooling update kits, is no longer active.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 15 of 19 C S.I. 1143 NOTE Dimension B in Figure A­1 correlates to Dimension B in Figure 2 and the values for Dimension B in Table1.
Figure A­1 Dimensions of New Spacers for Fixture P/N 64878 A new set­master ST­94­10 is necessary for the counterweight bushing location gage ST­94. Figure A­2 shows the finish grinding dimensions for the new set­master ST­94­10. You must make a stamp or do a vibra­peen etch of the step height dimension on each step, as shown in Figure A­2. This dimension is the distance from the centerline of the set­master to the surface of the step which can be compared to Dimension A in Table 1 of this Service Instruction. The counterweight bushing location gage ST­94 is made from oil hardened tool steel and ground to the finished dimensions. MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 16 of 19 C S.I. 1143 Figure A­2 Dimensions of New Set­Master P/N ST­94­10 To make sure the counterweight is correctly and squarely attached to the counterweight squareness gage ST­91, spacers have been added. These spacers are made from hardened steel and ground to finished dimensions. Refer to Figure A­3 and Table A­2 for special tool detail, part numbers, finished dimensions, and application of these spacers.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 17 of 19 C S.I. 1143 Figure A­3 Dimensions of New Spacers for the Counterweight Squareness Gage ST­91 TABLE A­2 DIMENSIONS OF NEW SPACERS FOR ST­91 GAGE SPACERS ST­91­7 ST­91­8 ST­91­9 ST­91­10 ST­91­11 ST­91­12 ST­91­13 ST­91­14 DIMENSION “C” FROM FIGURE A­3 IN. MM 5/64 1.98 11/64 4.37 13/64 5.16 7/64 2.79 7/32 9/64 1/32 1/4 5.56 3.57 0.79 6.35 USE WITH COUNTERWEIGHT P/N 73643, 73644, 72534, 73812 72801, LW­19225E, LW­19226E 71904, 71905, LW­19210 LW­19225D, LW­19226D, 75637, 14U22538 LW­19227D LW­19211, LW­19227E, 14U22539 LW­19212 75636, 76044, 78988 Different tools and set­up procedures are necessary for counterweights identified with the letter “E” as a suffix to the part number. These changes are: 1. Use spacers shown in Table 1 for Figure 2 of this Service Instruction. NOTE Use a 0.001 in. (0.025 mm) thick shim stock between the fixture P/N 64878 and the spacer P/N 64878­30 to align the counterweight P/N LW­19227E. 2. To do a check of the distance from the centerline of the bushing bore to the flat edge of the counterweight P/N LW­19227E with the fixture ST­94, use the 0.0761 in. (19.33 mm) step of the set­master ST­94­10. Refer to Figure A­2.
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 18 of 19 C S.I. 1143 3. Set the preloaded dial indicator to ± 0.001 in. (0.025 mm) to compensate for the 0.001 in. (0.025 mm) difference between the counterweight measurement and the set­master. 4. Figure A­4 shows an undercut to the knurled screw ST­91­6. This undercut is necessary to allow the use of existing spacers with the revised counterweights. Figure A­4 Modifications to the Knurled Screw ST­91­6
MO 12 ISSUED DAY YEAR 24 65 MO 11 REVISED DAY YEAR 10 11 PAGE NO. REVISION 19 of 19 C S.I. 1143